vat_rates_update

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are present, so the description carries the full burden of behavioral disclosure. It discloses a key side-effect: changing the rate percentage does not retroactively affect existing invoices, and that setting isDefault demotes any existing default (also documented in schema). It doesn't mention permission requirements or reversibility, but the description adds meaningfully useful behavioral context beyond what's implied by 'update'.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three concise, information-dense sentences with no filler. Front-loaded with the core purpose, followed by the key caveat about non-retroactivity, then the field scope and the required-field constraint. Every sentence earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema and no annotations, the description covers the core behavioral nuances well: non-retroactive rate changes, the updatable field set, and the 'at least one field' constraint. It could mention whether the operation is reversible or idempotent, and the companyId override nuance is only in the schema, not the description. For a simple update tool with a clean schema, this is reasonably complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3. All seven parameters have descriptions in the schema (VAT percentage, UUID to update, display label, display order, company override, default demotion, category code enum values). The description adds minor context like 'at least one field must be provided' but does not add significantly beyond the schema's own parameter descriptions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a clear action ('Update an existing VAT rate') on a specific resource (VAT rate), and explicitly lists the updatable fields (display label, category code, default status, position). It differentiates from create/delete siblings via the word 'existing' and update framing. However, it doesn't explicitly name sibling tools like vat_rates_create or vat_rates_delete, though the purpose is clear enough by context.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear context on scope: it only updates certain fields and explicitly excludes the rate percentage from being a separately-updated retroactive effect ('changing the rate percentage does not retroactively affect existing invoices'). It states the 'at least one field must be provided' constraint. It doesn't explicitly say 'use this instead of vat_rates_create' but the behavioral distinction is reasonably clear for an update tool.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.